In a conventional epicyclic bevel gear train transmission numerous arrangements are possible to secure different output shaft speeds in relation to input shaft speed. In one example, the input shaft drives one bevel side gear in one direction, a separate variable speed drive (belt drive, worm drive, e.g.) drives the other bevel side gear in the opposite direction, and the spider or crosshead having bevel pinions meshing with both side gears drives the output shaft at a speed depending on the relative speeds of the side gears. The output shaft and spider or crosshead remain stationary when the speeds of the side gears are equal in opposite directions.
In a conventional epicyclic spur gear train transmission numerous arrangements are possible to secure different output shaft speeds in relation to input shaft speed. In one example, the input shaft drives the sun gear, a variable speed drive driven by the input shaft drives the ring gear in the same direction as the sun gear, and the carrier for the planet gears that mesh with the ring and sun gears drives the output shaft in either direction depending on the relative speeds of the sun and ring gears. At a certain relative speed of the sun and ring gears the output shaft and planet gear carrier will remain stationary. In another example, the input shaft drives the sun gear, a separate variable speed drive drives the planet gear carrier, and the ring gear drives the output shaft.